1. Field of the Invention
This invention relates to a computer interface unit for a computer data print-out system using stencil printers with a stencil master making means, and more particularly to a computer interface unit which is connected between a computer such as a personal computer and a plurality of stencil printers, each provided with a stencil master making means, in a computer data print-out system.
2. Description of the Related Art
Recently, data made by a personal computer is often printed out by a printer. When printing out character data and/or image data made by a personal computer, a printer driver exclusive for a particular type of printer is installed in the personal computer. The printer driver converts the character data and the like made by the personal computer to resolution-dependent raster image data which conform to the resolution of the printer in response to print command from the application side and makes resolution-dependent print data including the raster image data and print control data. The printer driver inputs the resolution-dependent print data thus made into the printer and causes the printer to print out the data made by the personal computer.
Further, there has been known a stencil printer which reads out an image on an original to make image data and prints out a number of copies of the original on the basis of the image data. Further there has been proposed a printing system including a stencil printer which makes print according to print data output from a personal computer. Such a system will be referred to as xe2x80x9ca computer data print-out system using a stencil printerxe2x80x9d, in this specification.
FIG. 10 shows an example of a conventional computer data print-out system using a stencil printer which carries out printing according to print data output from a personal computer. The system comprises a personal computer 1, a stencil printer 3 with a stencil master making means and a computer interface unit 2 connected between the personal computer 1 and the stencil printer 3. The computer interface unit 2 receives resolution-dependent print data from the personal computer 1, makes page print data (output data) for the stencil printer 3 on the basis of address data, raster image data, page discharge data and the like in the resolution-dependent print data, and inputs the output data into the stencil printer 3. The stencil printer 3 makes a stencil master according to the output data input from the computer interface unit 2 and outputs copies by use of the stencil master. Further it is possible to cause the stencil printer 3 to make print according to print data output from a remote personal computer 4 by effecting data transfer through modems 5a and 5b. 
In the conventional system, the computer interface unit and the stencil printer are connected in one-to-one correspondence and the personal computer makes print data conforming to the resolution of the stencil printer connected to the computer interface unit with the computer interface unit generally not provided with resolution changing function. Accordingly, in a system where stencil printers of different resolutions, e.g., 300 dpi, 400 dpi and 600 dpi, are selectively connected to the computer interface unit, image information cannot be output in correct print positions and deformation of the image such as expansion and contraction of the image or image avalanche can be generated in the printed image if the resolution of the stencil printer actually connected to the computer interface unit differs from that the personal computer has expected.
Further, in the case where the personal computer can make print data only in a predetermined resolution, it is possible to arrange the computer interface unit to convert the resolution of the print data as output from the personal computer to that for a stencil printer which is expected to be connected to the computer interface unit. However also in this case, if a stencil printer of different resolution is connected to the computer interface unit, normal printing cannot be obtained.
Further when print data output from a remote personal computer which is connected to the computer interface unit through, for instance, modems, is to be printed, the operator of the personal computer cannot know the resolution of the stencil printer and it is difficult for the operator to conform the print data to the resolution of the stencil printer.
In view of the foregoing observations and description, the primary object of the present invention is to provide a computer interface unit for a computer data print-out system using stencil printers which enables the computer data print-out system to print out computer data made by the computer in a high quality free from deformation of the image such as expansion and contraction of the image or image avalanche even if the computer data is made without taking into account the output resolution of the stencil printer.
In accordance with a first aspect of the present invention, there is provided a computer interface unit for a computer data print-out system comprising a computer, a plurality of stencil printers each having a stencil master making means and a computer interface unit connected between the computer and the stencil printers, the computer interface unit being for making output data on the basis of raster image data and input resolution data representing the resolution of the raster image data which are input from the computer and outputting the output data into one of the stencil printers, said computer interface unit characterized by having
a printer resolution read-out means which reads out from each of the stencil printers the output resolution data representing the output resolution at which the stencil printer can make print, and
a data output means which selects out of the stencil printers connected to the computer interface unit a stencil printer which has an output resolution equal to the resolution of the raster image data on the basis of the input resolution data and the output resolution data representing the output resolution of each of the stencil printers, and outputs the output data into the selected stencil printer.
The computer interface unit of the first aspect of the present invention may deal with the case where there is no stencil printer which has an output resolution equal to the resolution of the raster image data in various manners. For example, the computer interface unit may give the alarm to the effect that there is no stencil printer which has an output resolution equal to the resolution of the raster image data, for instance, by generating alarm sound or sending a message to the computer without outputting the output data to any stencil printer.
In accordance with a second aspect of the present invention, there is provided a computer interface unit for a computer data print-out system comprising a computer, a plurality of stencil printers each having a stencil master making means and a computer interface unit connected between the computer and the stencil printers, the computer interface unit being for making output data on the basis of raster image data and input resolution data representing the resolution of the raster image data which are input from the computer and outputting the output data into one of the stencil printers, said computer interface unit characterized by having
a printer resolution read-out means which reads out from each of the stencil printers the output resolution data representing the output resolution at which the stencil printer can make print, and
a resolution conversion means which selects out of the stencil printers connected to the computer interface unit a stencil printer which has an output resolution conforming to the resolution of the raster image data on the basis of the input resolution data and the output resolution data representing the output resolution of each of the stencil printers, and converts the raster image data input from the computer to raster image data of resolution equal to the resolution of the selected stencil printer,
an output data making means which makes output data on the basis of the converted raster image data, and
a data output means which outputs the output data made by the output data making means into the selected stencil printer.
In the computer data print-out system of the present invention, a stencil printer having a stencil master making section formed integrally with a printing section is employed. The stencil master making section is provided with, for instance, a line type thermal head and perforates a stencil master material according to an image signal, thereby making a stencil master. The printing section has a printing drum around which the stencil master is wound and ink supplied inside the printing drum is transferred to a printing paper through perforations in the stencil master. In the stencil printer with such a stencil master making section, the resolution of the thermal head governs the resolution of the stencil printer.
The expression xe2x80x9ca stencil printer which has an output resolution conforming to the resolution of the raster image dataxe2x80x9d means one of the stencil printers connected to the computer interface unit which, when makes print on the basis of the output data made by the output data making means on the basis of the converted raster image data, can output an image the highest in quality in the stencil printers connected to the computer interface unit. For example, a stencil printer whose output resolution is an integral multiple of the resolution of the input raster image data is most preferable as the xe2x80x9cstencil printer which has an output resolution conforming to the resolution of the raster image dataxe2x80x9d. When there is connected no stencil printer whose output resolution is an integral multiple of the resolution of the input raster image data, the stencil printer which is the highest in output resolution in the stencil printers connected to the computer interface unit is selected.
When a stencil printer whose output resolution is identical to the resolution of the input raster image data is connected to the computer interface unit, the stencil printer may be selected as the xe2x80x9cstencil printer which has an output resolution conforming to the resolution of the raster image dataxe2x80x9d. In this case, the resolution conversion means may input into the output data making means the input raster image data as it is without resolution conversion. However, in this specification, it should be broadly interpreted that the resolution conversion means converts the raster image data input from the computer to raster image data of resolution equal to the resolution of the selected stencil printer even if a stencil printer whose output resolution is identical to the resolution of the input raster image data is selected as the xe2x80x9cstencil printer which has an output resolution conforming to the resolution of the raster image dataxe2x80x9d and the resolution conversion inputs into the output data making means the input raster image data as it is without resolution conversion. Further the resolution conversion means may select a stencil printer whose output resolution is an integral multiple of the resolution of the input raster image data as the xe2x80x9cstencil printer which has an output resolution conforming to the resolution of the raster image dataxe2x80x9d even if a stencil printer whose output resolution is identical to the resolution of the input raster image data is connected to the computer interface unit.
In the computer data print-out system of the first aspect of the present invention, since a stencil printer which has an output resolution equal to the resolution of the raster image data is selected out of the stencil printers connected to the computer interface unit and the selected stencil printer makes print, high quality printing free from deformation of the image such as expansion and contraction of the image or image avalanche can be obtained.
Further in the computer data print-out system of the second aspect of the present invention, when there is connected no stencil printer whose output resolution is equal to the resolution of the raster image data, a stencil printer which has an output resolution conforming to the resolution of the raster image data is selected out of the stencil printers connected to the computer interface unit and the selected stencil printer makes print, whereby high quality printing relatively free from deformation of the image such as expansion and contraction of the image or image avalanche can be obtained.
In the case where a resolution optimal to desired printing can be selected by the computer side printer driver, printing of as high quality as possible can be obtained by simply selecting the optimal resolution by the computer side printer driver since a stencil printer which has an output resolution conforming to or equal to the optimal resolution is automatically selected and caused to make print.